There is a need for a method and apparatus which provides a signal corresponding to the number of revolutions of an axle. Such need requires that the signal is obtained in a contactless manner and causes little wear to the apparatus. It is also preferable if the apparatus is insensitive to contamination and humidity and can also respond to high accelerations and a high number of revolutions. Finally, there is a need that the apparatus should also respond to small angular increments as well as the number of revolutions of the axle. In any case, the apparatus should be easily and inexpensively manufactured.
It is an object of the present invention, therefore, to provide a method and apparatus which yields a value corresponding to the number of revolutions or the angle of rotation of an axle.
It is also an object of the present invention to provide such an apparatus in which the number of revolutions or angle of rotations is developed in a contactless manner and which apparatus is insensitive to contamination and humidity.
It is still a further object of the present invention to provide a method and device for yielding a signal corresponding to the number of revolutions or angle of rotation of an axle which can respond to high accelerations, a high number of revolutions, and is readily and inexpensively manufacturable.